Objects of class high_resolution_clock represent clocks with the shortest tick period. high_resolution_clock may be a synonym for system_clock or steady_clock.
class high_resolution_clock {
public:
typedef unspecified rep;
typedef ratio<unspecified, unspecified> period;
typedef chrono::duration<rep, period> duration;
typedef chrono::time_point<unspecified, duration> time_point;
static const bool is_steady = unspecified;
static time_point now() noexcept;
};